1. Field of the Invention
The present invention relates to a process for the production of a wholly aromatic polyester carbonate. More particularly, it relates to a process for producing, with good productivity, a wholly aromatic polyester carbonate that has low coloration and a high degree of polymerization by combining a prepolymerization step, a crystallization step, and a solid-phase polymerization step using a specific aromatic dicarboxylic acid, aromatic diol, and diaryl carbonate as starting materials.
Furthermore, the present invention relates to a wholly aromatic polyester carbonate. More particularly, it relates to a wholly aromatic polyester carbonate that has specific terminal groups, and has low coloration and a high degree of polymerization.
2. Description of the Related Art
In recent years, there has been a desire for enhanced performance in engineering plastics having high heat resistance and excellent mechanical strength. Amorphous engineering plastics include polyarylates and polycarbonates.
Wholly aromatic polyesters (polyarylates) have excellent heat resistance and chemical resistance, but have the problems that the melt viscosity is high and the moldability is poor. On the other hand, aromatic polycarbonates are inferior in terms of heat resistance and chemical resistance, but their moldability is excellent and they find widespread application. By introducing a carbonate bond into a wholly aromatic polyester, the effect of improving the flowability of the wholly aromatic polyester can be expected, and it is therefore important to develop a process for the production of such an aromatic polyester carbonate.
With regard to a process for the production of an aromatic polyester carbonate, a melt polymerization method has been known for a long time, but since the viscosity increases during the second half of the reaction it is difficult to obtain a polymer having a high degree of polymerization. Furthermore, since the polymerization reaction is carried out at high temperature, there is the problem that coloration occurs.
Because of this, a solid-phase polymerization method for an aromatic polyester carbonate has been investigated. The solid-phase polymerization method is a method that involves synthesis of a prepolymer having a certain degree of polymerization by melt polymerization, crystallization of the prepolymer by means of heating, treating with a solvent, etc., and subsequent polymerization in a solid phase.
As one example of the solid-phase polymerization method for an aromatic polyester carbonate, a method in which a dicarboxylic acid, a diol, and a diaryl carbonate are subjected to a hot-melt reaction to give a prepolymer, which is then subjected to a solid-phase polymerization has been reported (JP-A-55-98224 (JP-A denotes a Japanese unexamined patent application publication)). In this method, however, the solubility of the aromatic dicarboxylic acid is low, dissolving the dicarboxylic acid is thus a rate-determining step, and since the reaction must be carried out at high temperature and requires a long period of time, there is a limit to the improvement in the coloration.
On the other hand, consideration has also been given to crystallizing the prepolymer and then subjecting it to solid-phase polymerization. With regard to crystallization of a polyacrylate prepolymer, a method in which treatment is carried out using a specific crystallizing agent has been reported (JP-A-5-331270 and JP-A-5-331271). However, this method employs an excess amount of crystallizing agent relative to the prepolymer, and removal of this crystallizing agent entails considerable expense.
With regard to other methods for crystallizing the prepolymer, a method in which the prepolymer in a molten state is cooled to a temperature at which crystallization proceeds at a sufficiently high speed, a method in which it is heated from room temperature to that temperature (JP-A-53-35796), etc. have been reported. However, in these methods, since the prepolymer has a long thermal history, there is the problem of progressive coloration of the prepolymer.
With regard to solid-phase polymerization methods for a wholly aromatic polyester, for example, methods have been reported in which an aromatic diol and a diaryl aromatic dicarboxylate ester are reacted (JP-A-5-331270), or an aromatic diol ester derivative and an aromatic dicarboxylic acid are reacted (JP-A-5-331271) to give a prepolymer, which is then crystallized in a crystallizing solvent by applying high shear, followed by a solid-phase polymerization.
However, all these methods require esterification of a starting material in advance, and there is the problem of high cost.
With regard to solid-phase polymerization methods for an aromatic polyester carbonate, there are methods in which a prepolymer is produced from an aromatic diol, an aromatic dicarboxylic acid, and a diaryl carbonate, and the prepolymer thus obtained is crystallized and then subjected to solid-phase polymerization (JP-A-1-247420, etc.). However, in these methods, since the crystallized prepolymer used in the solid-phase polymerization is in the form of a powder, there is a serious problem in handling during the process. In addition, there is a limit to reducing the solid-phase polymerization time in the solid-phase polymerization method employing a crystallized prepolymer in the form of a powder.
As described above, it has been difficult in practice to produce a high molecular weight polymer in a short period of time with low cost and without any problems in handling by the conventionally known solid-phase polymerization method for a wholly aromatic polyester carbonate.
It is a first object of the present invention to provide an industrial and economical production process for obtaining a high molecular weight wholly aromatic polyester carbonate that is transparent and has low coloration, has good physical properties, and can melt at a comparatively low temperature to become amorphous, using an aromatic dicarboxylic acid, an aromatic diol, and a diaryl carbonate as starting materials directly without needing to esterify the aromatic dicarboxylic acid and aromatic diol in advance. Furthermore, it is to provide a process for the production of a wholly aromatic polyester carbonate, in which handling in the production steps is easy, and the time required for solid-phase polymerization is short.
Moreover, it is a second object of the present invention to provide a high molecular weight wholly aromatic polyester carbonate having a specific terminal group, and which is transparent, has low coloration and good physical properties, and can melt at a comparatively low temperature to become amorphous.
The above-mentioned objects are accomplished by the following means.
A first aspect of the present invention relates to a process for the production of a wholly aromatic polyester carbonate as follows.
A process for the production of a wholly aromatic polyester carbonate using three components, that is, an aromatic diol component (a) represented by formula (I) below
HOxe2x80x94Ar1xe2x80x94Xxe2x80x94Ar2xe2x80x94OHxe2x80x83xe2x80x83(I) 
{in formula (I), Ar1 and Ar2 are each phenylene groups, which may be substituted, and X is a divalent organic group represented by formula (II) below 
(here, R1, R2, R3, and R4 are each independently chosen from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbons, a cycloalkyl group having 5 or 6 carbons, an aryl group having 6 to 12 carbons, and an aralkyl group having 7 to 12 carbons, q denotes an integer of 4 to 10, and q each of R3 and R4 may be identical or different)}, an aromatic dicarboxylic acid component (b), and a diaryl carbonate (c) in molar ratios that simultaneously satisfy expressions (1), (2), and (3) below
A:B:C=(1+X1):1:(2+X2)xe2x80x83xe2x80x83(1) 
0.9xe2x89xa6C/(A+B)xe2x89xa61.1xe2x80x83xe2x80x83(2) 
0.5xe2x89xa6X2/X1xe2x89xa61.5xe2x80x83xe2x80x83(3) 
(in the expressions, A denotes the number of moles of the aromatic diol component (a), B denotes the number of moles of the aromatic dicarboxylic acid component (b), and C denotes the number of moles of the diaryl carbonate (c). X1 and X2 denote any number that is larger than 0 and at most 0.5, and may be identical or different), characterized in that a high molecular weight polymer is obtained by carrying out, in sequence,
1) a prepolymerization step in which a prepolymer is prepared by prepolymerizing the three components, that is, the above-mentioned aromatic diol component (a), aromatic dicarboxylic acid component (b), and diaryl carbonate (c) while heating at a temperature of at least 180xc2x0 C. using, as the aromatic dicarboxylic acid component (b), terephthalic acid (bxe2x80x2) alone or an aromatic dicarboxylic acid component mixture (bxe2x80x3) of terephthalic acid and isophthalic acid at a molar ratio that satisfies expression (4) below
0xe2x89xa6IA/TA less than 1xe2x80x83xe2x80x83(4) 
(in the expression, TA and IA are the numbers of moles of terephthalic acid and isophthalic acid, respectively),
2) a crystallization step in which the prepolymer is crystallized to prepare a crystallized prepolymer, and
3) a solid-phase polymerization step in which the degree of polymerization of the crystallized prepolymer is increased.
Furthermore, a second aspect of the present invention relates to a wholly aromatic polyester carbonate as follows.
A wholly aromatic polyester carbonate characterized in that a repeating unit represented by formula (V) below
Axe2x80x94(COxe2x80x94Ar3xe2x80x94COOxe2x80x94Ar1xe2x80x94Xxe2x80x94Ar2xe2x80x94O)100xe2x80x94(COOxe2x80x94Ar1xe2x80x94Xxe2x80x94Ar2xe2x80x94O)100X3xe2x80x94Bxe2x80x83xe2x80x83(V) 
{in formula (V), Ar1 and Ar2 are each phenylene groups, which may be substituted, Ar3 is an aromatic group, which may be substituted, X is a divalent organic group represented by formula (II) below 
(here, R1, R2, R3, and R4 are each independently chosen from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbons, a cycloalkyl group having 5 or 6 carbons, an aryl group having 6 to 12 carbons, and an aralkyl group having 7 to 12 carbons, q denotes an integer of 4 to 10, and q each of R3 and R4 may be identical or different), and X3 is a number greater than 0 and at most 0.5}
is random copolymerized, and terminal groups A and B of the molecule are groups chosen from the group consisting of an aryloxy group, which may be substituted with a halogen atom or a methyl group, a hydroxyaryl group, which may have a substituent, and a carboxyaryl group, which may be substituted.